Smallpox didn't mutate that much, right?
That's true Smallpox was a DNA virus as opposed to RNA viruses like Coronavirus. DNA viruses are much less prone to mutations.
Monkeypox is a DNA virus.
Also, Smallpox didn't have an animal reservoir. It only infected people making it much easier to wipe out.
"Monkeypox virus can infect a wide range of mammal species, including monkeys, anteaters, hedgehogs, prairie dogs, squirrels, and shrews.
"We are still learning which species of animals can get monkeypox. While we do not know if reptiles, amphibians, or birds can get monkeypox, it is unlikely since these animals have not been found to be infected with other orthopoxviruses.
"Monkeypox could establish new reservoirs in animals Concern grows that virus will get footholds in species outside Africa.